Young, religiously active people are more likely than their non-religious counterparts to become obese in middle age, according to new research. In fact, frequent religious involvement appears to almost double the risk of obesity compared with little or no involvement.

What is unclear from the new research is why religion might be associated with overeating.

"Churches pay more attention to obvious vices like smoking or drinking," said Matthew Feinstein, lead author of the research and fourth-year medical student at Northwestern University Feinberg School of Medicine. "Our best guess about why is that...more frequent participation in church is associated with good works and people may be rewarding themselves with large meals that are more caloric in nature than we would like."

The new research, presented at an American Heart Association conference dedicated to physical activity, metabolism and cardiovascular disease, involved 2,433 people enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. The group was tested - at first between 20 and 32 years old - for various cardiovascular disease risk factors such as diabetes, hypertension, and smoking. Those same tests were repeated in the same group over the next 25 years.

The results were mixed for many risk factors for cardiovascular disease, but as researchers analyzed the data, one disparity stood out. Those who reported attending church weekly, or more often, were significantly more likely to have a higher body mass index than those who attended infrequently, or never.

Kenneth F. Ferraro, author of similar studies linking obesity with religion, suggested that marriage may have played a role in the weight gain.

"The time period studied is when many Americans get married," said Ferraro, director of the Center on Aging and the Life Course at Purdue University. "We know that weight gain is common after marriage and that marriage is highly valued in most religious groups. Thus, one wonders if the results could be partially due to religious people being more likely to get married earlier and then gaining weight."

Those church potlucks probably don't help either.

"There's certainly a church culture around eating," said Erik Christensen, a pastor at St. Luke's Lutheran Church of Logan Square in Chicago, Illinois. "What I see among congregants in their 20s and 30s is they are very fit and what I see among congregants in their 50s and 60s is disproportionate obesity."

Christensen suggested that the virtual disappearance of church-sponsored baseball and basketball leagues may be part of the problem. He added that the decision to attend church is sometimes made at the expense of being involved in athletic or recreational activities.

But he kept coming back to that culture of eating.

"What's ironic to me is that in my congregation we are working on a childhood obesity initiative and spend a lot of time thinking about weight and food," said Christensen. "We sit and have a potluck and talk about obesity."

Yet another irony is the number of studies suggesting that religion and faith are actually beneficial for health. Recent studies suggest that a "relaxation response" in the brain among people who pray, meditate, or engage in otherwise relaxing activities may alleviate anxiety and stress. Stress is implicated in many illnesses. Other studies suggest an association between church-going and longevity.

"On the whole being religious has been shown by many studies to be associated with better mental health, lower smoking rates, lower mortality rates and better overall health status," said Feinstein. "There are a whole lot of things religious people are doing right, but it's just this specific area where there appears to be room for improvement."

The upshot of the new research, said Feinstein, is that knowing there may be an obesity problem among church-goers provides a captive audience for intervention.

"The real value of the study is not understanding why," said Feinstein. "What this study does is highlights a group that could potentially benefit from targeted anti-obesity initiatives. That's exciting because there is a lot of infrastructure already in place in religious communities."